title: Effects of solvents, ligand aromaticity, and coordination sphere on the g tensor of anionic o-semiquinone radicals complexed by Mg2+ ions: DFT studies.
abstract: Density functional theory (DFT) was employed to study the impact of Mg(2+) ions on the o-semiquinone radical anions of different aromaticity in protic and aprotic solvents. After the geometry optimization of ligands and complexes, their g tensors were computed at the UBP86/TZVP and UB3LYP/TZVP theory levels. The suitability of various model systems, assuming continuum dielectric approaches, different Mg(2+) coordination spheres (completed by solvent molecules), and inclusion of additional solvent molecules H-bonded to the ligands, was tested in terms of correlation between the experimental and calculated g-shifts. The effects of complexation, ligands aromaticity, and solvents on the electron spin density for o-semiquinones are discussed. To recognize clearly the changes in the nature of the g tensor components, the contributions from particular excited states were analyzed. A structural characterization of the tested complexes is expected to be helpful in investigations on the complicated biosystems in which the similar paramagnetic units are present.
authors.affiliation: Faculty of Chemistry, Wroclaw University, Wroclaw, Poland. mck@eto.wchuwr.pl
authors.forename: Maciej
authors.initials: M
authors.lastname: Witwicki
authors.forename: Julia
authors.initials: J
authors.lastname: Jezierska
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D016227:Benzoquinones / Q000737:chemistry*; D001665:Binding Sites; D004583:Electrons; D006860:Hydrogen Bonding; D008024:Ligands; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000097:Acetonitriles; D016227:Benzoquinones; D008024:Ligands; D012997:Solvents; D014867:Water; C025232:semiquinone radicals; D008274:Magnesium; C032159:acetonitrile